Have you ever played a map and noticed that brushes such as chairs and other furniture are twice as big as they should be? This results when a map is constructed by a younger person. You see, if a 9 year old and a 17 year old both made a map of the same kitchen, the 9 year old's oven, table, etc. would be a lot bigger because that's how he views things in real life. If you play DM-Christmas Streets for instance, you can tell that map was made by a little kid because the couches are head-high! If you are younger, you should probably check your maps to make sure they're in the right proportions. One good way to do this is to play the map in third-person view mode. If your player model is a human adult, doors and stuff start to look a bit silly when 128 high. Of course this isn't to important if you're making a castle level or something, but if you are constucting a realism map, you might want to look into it.